Module 8: The structure and function of the cardiovascular system

The Body in Action

1. Introduction to the cardiovascular system
2. The heart
   1. Structure of the heart
   2. The heart valves
3. Labelling the heart activity
4. Circulatory system
   1. Animation of the circulation systems
5. Blood vessels
   1. Arteries
   2. Capillaries
   3. Veins
6. Characteristics of blood vessels activity
7. Function of the cardiovascular system
8. Function of the blood

Circulatory system

The vascular system has two pathways of circulation, the pulmonary circulation (to the lungs) and the systemic circulation (to the body).

Pulmonary circulation

This is the flow of blood from the right side of the heart to the lungs and then back to the left side of the heart. The right atrium collects deoxygenated blood that is returning from the body via two large veins the inferior and superior vena cava. The blood then moves from the right atrium into the right ventricle. From the right ventricle the deoxygenated blood is pumped to the lungs through the pulmonary artery. Within the lungs pulmonary diffusion takes place, the blood is enriched with oxygen and carbon dioxide is removed before the blood returns to the heart via the pulmonary vein.

Systemic circulation

This is the flow of blood from the left side of the heart to all parts of the body and then back into the right side of the heart. The left atrium receives oxygenated blood from the lungs via the pulmonary vein. The blood then moves into the left ventricle. This oxygenated blood is then pumped through the aorta (the largest artery in the body) to the rest of the body. It transports the oxygen and nutrients to the working muscles, internal organs and all other living tissues within the body.

The muscular walls of the left ventricle are three times thicker than those of the right; this is because the left ventricle is responsible for pumping blood all round the body, whereas the right ventricle is only responsible for pumping blood to the lungs.